In 1960 Louis Kahn’s theoretical concerns began to focus on a concept which he called “form”, not meaning a building’s three dimensional shape, but the essence of its underlying type. The current study considers Kahn’s post-1960 concept of “form”, as espoused in his 1961 article, “Form and Design”, in relation to Plato’s theory of Forms, as that theory is presented in The Republic. A deeper appreciation of Kahn’s text is achieved through an examination of the hypothesis that the word “form”, as it is defined in Kahn’s article, is congruous with Plato’s famous concept, whereby Forms are said to be independent of humans and particulars. This leads to a related hypothesis, that Kahn’s shift in emphasis towards transcendent types is reflected in his development of what could be called Platonising architectural strategies, because they reflect parallel aims between Plato and Kahn. While Kahn and Plato are quite different figures, separated by time, profession and intentions, consideration of Plato’s treatment of the Forms in The Republic illuminates a new interpretation of “Form and Design” and the building which is most closely associated with that text, Kahn’s First Unitarian Church and School in Rochester. The thesis identifies ideas within Kahn’s text which resonate with Plato’s philosophy, suggesting that Kahn’s theory can be interpreted through notions stemming from the early moments of the Western philosophical tradition. It also identifies inconsistencies between Kahn’s text and Plato’s and between various statements made by Kahn, highlighting the fact that Kahn’s philosophical musings are not those of a trained philosopher.